DESCRIPTION: (Taken from application) The goal of the proposed research is to enhance the understanding of the dissolution bioavailability, and remediation of complex, multi- component, dense non-aqueous-phase immiscible organic liquids (DNAPLs) in sub-surface system. The specific objectives are: (1) investigate the effects of DNAPL composition and mass-transfer constrains on the dissolution of complex (multi-component) DNAPL; (2) investigate the bioavailability and biodegradation of complex DNAPLs; (3) investigate the effect of solubilization agents on the dissolution and bioavailability of complex DNAPLs; (4) develop and evaluate advanced mathematical models capable of simulating the dissolution, biodegradation, and transport of DNAPL constituents in heterogeneous porous media. These objectives are addressed by taking a multi-step approach where these factors will first be characterized separately, and then integrated by the combined use of "multiple-factor" experiments and mathematical modeling. We have developed systems that allow the simultaneous characterization of NAPL dissolution, contaminant transport and biodegradation, and microbial activity. For example, selected experiments will use a flow cell/fiber optic detection system that has been equipped with multiple sensors and detectors. The results of the proposed research will enhance our understanding of the dissolution and bioavailability of DNAPL mixtures in subsurface system. These results would significantly improve the ability to conduct accurate risk assessments of the potential human-health-related impacts of contaminated sites. Furthermore, the results will assist in related impacts of contaminated sites. Furthermore, the results will assist in the design and implementation of more effective remediation systems. The results will also be pertinent to the issue of alternative, risk-based clean-up standards.